Chromosome 21

Last updated
Chromosome 21
Human male karyotpe high resolution - Chromosome 21 cropped.png
Human chromosome 21 pair after G-banding.
One is from the mother, one is from the father.
Human male karyotpe high resolution - Chromosome 21.png
Chromosome 21 pair
in human male karyogram.
Features
Length (bp)45,090,682 bp
(CHM13)
No. of genes 215 (CCDS) [1]
Type Autosome
Centromere position Acrocentric [2]
(12.0 Mbp [3] )
Complete gene lists
CCDS Gene list
HGNC Gene list
UniProt Gene list
NCBI Gene list
External map viewers
Ensembl Chromosome 21
Entrez Chromosome 21
NCBI Chromosome 21
UCSC Chromosome 21
Full DNA sequences
RefSeq NC_000021 (FASTA)
GenBank CM000683 (FASTA)

Chromosome 21 is one of the 23 pairs of chromosomes in humans. Chromosome 21 is both the smallest human autosome and chromosome, [4] with 46.7 million base pairs (the building material of DNA) representing about 1.5 percent of the total DNA in cells. Most people have two copies of chromosome 21, while those with three copies of chromosome 21 (trisomy 21) have Down syndrome.

Contents

Researchers working on the Human Genome Project announced in May 2000 that they had determined the sequence of base pairs that make up this chromosome. [5] Chromosome 21 was the second human chromosome to be fully sequenced, after chromosome 22.

Genes

Number of genes

The following are some of the gene count estimates of human chromosome 21. Because researchers use different approaches to genome annotation, their predictions of the number of genes on each chromosome varies (for technical details, see gene prediction). Among various projects, the collaborative consensus coding sequence project (CCDS) takes an extremely conservative strategy. Thus CCDS's gene number prediction represents a lower bound on the total number of human protein-coding genes. [6]

Estimated by Protein-coding genes Non-coding RNA genes Pseudogenes SourceRelease date
CCDS 212 [1] 2022-10-26
HGNC 215193194 [7] 2024-04-10
Ensembl 221447185 [8] 2023-07-17
UniProt 246 [9] 2024-10-02
NCBI 256356207 [10] [11] [12] 2017-05-19

Gene list

The following is a partial list of genes on human chromosome 21. For complete list, see the link in the infobox at the top of the article.

In addition, the chromosome has many genes for keratin-associated protein, with symbols: KRTAP6-1, KRTAP6-2, KRTAP6-3, KRTAP7-1, KRTAP8-1, KRTAP10-1, KRTAP10-2, KRTAP10-3, KRTAP10-4, KRTAP10-5, KRTAP10-6, KRTAP10-7, KRTAP10-8, KRTAP10-9, KRTAP10-10, KRTAP10-11, KRTAP10-12, KRTAP11-1, KRTAP12-1, KRTAP12-1, KRTAP12-2, KRTAP12-3, KRTAP12-4, KRTAP13-1, KRTAP13-2, KRTAP13-3, KRTAP13-4, KRTAP15-1, KRTAP19-1, KRTAP19-2, KRTAP19-3, KRTAP19-4, KRTAP19-5, KRTAP19-6, KRTAP19-7, KRTAP19-8, KRTAP20-1, KRTAP20-2, KRTAP20-3, KRTAP20-4, KRTAP21-1, KRTAP21-2, KRTAP21-3, KRTAP22-1, KRTAP22-2, KRTAP23-1, KRTAP24-1, KRTAP25-1, KRTAP26-1, KRTAP27-1.

Diseases and disorders

The following diseases and disorders are some of those related to genes on chromosome 21:

Chromosomal conditions

A karyotype of somebody affected with Down syndrome, depicting the presence of a full additional copy of chromosome 21. The presence of this extra copy is also referred to as Trisomy 21. Trisomie 21 Genom-Schema.gif
A karyotype of somebody affected with Down syndrome, depicting the presence of a full additional copy of chromosome 21. The presence of this extra copy is also referred to as Trisomy 21.

The following conditions are caused by changes in the structure or number of copies of chromosome 21:

Cytogenetic band

G-banding ideograms of human chromosome 21
Human chromosome 21 ideogram vertical.svg
G-banding ideogram of human chromosome 21 in resolution 850 bphs. Band length in this diagram is proportional to base-pair length. This type of ideogram is generally used in genome browsers (e.g. Ensembl, UCSC Genome Browser).
Human chromosome 21 - 400 550 850 bphs.png
G-banding patterns of human chromosome 21 in three different resolutions (400, [15] 550 [16] and 850 [3] ). Band length in this diagram is based on the ideograms from ISCN (2013). [17] This type of ideogram represents actual relative band length observed under a microscope at the different moments during the mitotic process. [18]
G-bands of human chromosome 21 in resolution 850 bphs [3]
Chr.Arm [19] Band [20] ISCN
start [21]
ISCN
stop [21]
Basepair
start
Basepair
stop
Stain [22] Density
21p13031113,100,000gvar
21p123116833,100,0017,000,000stalk
21p11.268310567,000,00110,900,000gvar
21p11.11056127410,900,00112,000,000acen
21q11.11274136712,000,00113,000,000acen
21q11.21367158413,000,00115,000,000gneg
21q21.11584201915,000,00122,600,000gpos100
21q21.22019214422,600,00125,500,000gneg
21q21.32144233025,500,00130,200,000gpos75
21q22.112330248530,200,00134,400,000gneg
21q22.122485261034,400,00136,400,000gpos50
21q22.132610270336,400,00138,300,000gneg
21q22.22703285838,300,00141,200,000gpos50
21q22.32858320041,200,00146,709,983gneg

Related Research Articles

<span class="mw-page-title-main">Chromosome 1</span> Human chromosome

Chromosome 1 is the designation for the largest human chromosome. Humans have two copies of chromosome 1, as they do with all of the autosomes, which are the non-sex chromosomes. Chromosome 1 spans about 249 million nucleotide base pairs, which are the basic units of information for DNA. It represents about 8% of the total DNA in human cells.

<span class="mw-page-title-main">Chromosome 6</span> Human chromosome

Chromosome 6 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 6 spans nearly 171 million base pairs and represents between 5.5 and 6% of the total DNA in cells. It contains the major histocompatibility complex, which contains over 100 genes related to the immune response, and plays a vital role in organ transplantation.

<span class="mw-page-title-main">Chromosome 13</span> Human chromosome

Chromosome 13 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 13 spans about 113 million base pairs and represents between 3.5 and 4% of the total DNA in cells.

<span class="mw-page-title-main">Chromosome 22</span> Human chromosome

Chromosome 22 is one of the 23 pairs of chromosomes in human cells. Humans normally have two copies of chromosome 22 in each cell. Chromosome 22 is the second smallest human chromosome, spanning about 51 million DNA base pairs and representing between 1.5 and 2% of the total DNA in cells.

<span class="mw-page-title-main">Chromosome 2</span> Human chromosome

Chromosome 2 is one of the twenty-three pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 2 is the second-largest human chromosome, spanning more than 242 million base pairs and representing almost eight percent of the total DNA in human cells.

<span class="mw-page-title-main">Chromosome 3</span> Human chromosome

Chromosome 3 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 3 spans more than 198 million base pairs and represents about 6.5 percent of the total DNA in cells.

<span class="mw-page-title-main">Chromosome 4</span> Human chromosome

Chromosome 4 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 4 spans more than 190 million base pairs and represents between 6 and 6.5 percent of the total DNA in cells.

<span class="mw-page-title-main">Chromosome 5</span> Human chromosome

Chromosome 5 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 5 spans about 182 million base pairs and represents almost 6% of the total DNA in cells. Chromosome 5 is the 5th largest human chromosome, yet has one of the lowest gene densities. This is partially explained by numerous gene-poor regions that display a remarkable degree of non-coding and syntenic conservation with non-mammalian vertebrates, suggesting they are functionally constrained.

<span class="mw-page-title-main">Chromosome 7</span> Human chromosome

Chromosome 7 is one of the 23 pairs of chromosomes in humans, who normally have two copies of this chromosome. Chromosome 7 spans about 160 million base pairs and represents between 5 and 5.5 percent of the total DNA in cells.

<span class="mw-page-title-main">Chromosome 8</span> Human chromosome

Chromosome 8 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 8 spans about 146 million base pairs and represents between 4.5 and 5.0% of the total DNA in cells.

<span class="mw-page-title-main">Chromosome 9</span> Human chromosome

Chromosome 9 is one of the 23 pairs of chromosomes in humans. Humans normally have two copies of this chromosome, as they normally do with all chromosomes. Chromosome 9 spans about 138 million base pairs of nucleic acids and represents between 4.0 and 4.5% of the total DNA in cells.

<span class="mw-page-title-main">Chromosome 10</span> Human chromosome

Chromosome 10 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 10 spans about 134 million base pairs and represents between 4 and 4.5 percent of the total DNA in cells.

<span class="mw-page-title-main">Chromosome 11</span> Human chromosome

Chromosome 11 is one of the 23 pairs of chromosomes in humans. Humans normally have two copies of this chromosome. Chromosome 11 spans about 135 million base pairs and represents between 4 and 4.5 percent of the total DNA in cells. The shorter arm is termed 11p while the longer arm is 11q. At about 21.5 genes per megabase, chromosome 11 is one of the most gene-rich, and disease-rich, chromosomes in the human genome.

<span class="mw-page-title-main">Chromosome 12</span> Human chromosome

Chromosome 12 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 12 spans about 133 million base pairs and represents between 4 and 4.5 percent of the total DNA in cells.

<span class="mw-page-title-main">Chromosome 14</span> Human chromosome

Chromosome 14 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 14 spans about 107 million base pairs and represents between 3 and 3.5% of the total DNA in cells.

<span class="mw-page-title-main">Chromosome 15</span> Human chromosome

Chromosome 15 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 15 spans about 99.7 million base pairs and represents between 3% and 3.5% of the total DNA in cells. Chromosome 15 is an acrocentric chromosome, with a very small short arm, which contains few protein coding genes among its 19 million base pairs. It has a larger long arm that is gene rich, spanning about 83 million base pairs.

<span class="mw-page-title-main">Chromosome 16</span> Human chromosome

Chromosome 16 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 16 spans about 90 million base pairs and represents just under 3% of the total DNA in cells.

<span class="mw-page-title-main">Chromosome 17</span> Human chromosome

Chromosome 17 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 17 spans more than 84 million base pairs and represents between 2.5 and 3% of the total DNA in cells.

<span class="mw-page-title-main">Chromosome 18</span> Human chromosome

Chromosome 18 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 18 spans about 80 million base pairs and represents about 2.5 percent of the total DNA in cells.

<span class="mw-page-title-main">Chromosome 19</span> Human chromosome

Chromosome 19 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 19 spans more than 61.7 million base pairs, the building material of DNA. It is considered the most gene-rich chromosome containing roughly 1,500 genes, despite accounting for only 2 percent of the human genome.

References

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  19. "p": Short arm; "q": Long arm.
  20. For cytogenetic banding nomenclature, see article locus.
  21. 1 2 These values (ISCN start/stop) are based on the length of bands/ideograms from the ISCN book, An International System for Human Cytogenetic Nomenclature (2013). Arbitrary unit.
  22. gpos: Region which is positively stained by G banding, generally AT-rich and gene poor; gneg: Region which is negatively stained by G banding, generally CG-rich and gene rich; acen Centromere. var: Variable region; stalk: Stalk.